jamieson Posted November 10, 2009 Report Share Posted November 10, 2009 (edited) Can anyone please help with this one? I recently bought a 247 Cota with engine partially stripped. The engine came with a new piston (to be fitted) which according to the the previous owner is a Bultaco piston. Apparently this can be fitted to the Cota but requires a shim/spacer plate (also supplied with the engine) at the base of the cylinder barrel, presumably because the piston height above the gudgeon pin is different? Anyway, my question is this.....has anyone else fitted a similar piston to a 247 Cota, and if so do you need to install a base gasket top and bottom of the spacer under the cylinder barrel? Hope this makes sense Cheers Simon Edited November 10, 2009 by Jamieson Quote Link to comment Share on other sites More sharing options...
dave dix Posted November 10, 2009 Report Share Posted November 10, 2009 Hi, i fitted an oversized bultaco piston to my 247 mont and i never used a base-plate. The piston was the same gudgeon pin height, if i remember correctly you put a window in the rear of the piston unless its all ready done and i did my own re-bore to size Dave Quote Link to comment Share on other sites More sharing options...
bridgwaterjohn Posted December 5, 2009 Report Share Posted December 5, 2009 Simon Have you had any luck in sorting out your piston. I have a montesa Cota 247 and i am strugling to find a piston, (72mm dia + 50 required) If you have sorted it out could you please let me have any details, ie piston numbers, and any modification you have had to make. Did your piston have any ports in the skirts ? Many thanks for your help Beast regards John H Quote Link to comment Share on other sites More sharing options...
pedronicman Posted December 5, 2009 Report Share Posted December 5, 2009 Hi, i fitted an oversized bultaco piston to my 247 mont and i never used a base-plate. The piston was the same gudgeon pin height, if i remember correctly you put a window in the rear of the piston unless its all ready done and i did my own re-bore to sizeDave Sherpa 250 models never had windows in the back of the piston , but there are 2 small holes at the front of the piston one on top of each other about 2mm in size. Also bultaco sherpa ring pegs are at the front of the piston and montesa ones are at the back. Quote Link to comment Share on other sites More sharing options...
dave dix Posted December 6, 2009 Report Share Posted December 6, 2009 Just got my old mont 247 piston and the ring pegs are at the front around 10 and 2 o'clock as were the bult piston. Piston fitted had a rear window and 2 small front holes, made by GPM of Italy. It works fine Dave Quote Link to comment Share on other sites More sharing options...
helm Posted December 6, 2009 Report Share Posted December 6, 2009 Hi try here in stock http://kevinbreedonracing.co.uk/profile.htm cheers helm Quote Link to comment Share on other sites More sharing options...
jamieson Posted December 14, 2009 Author Report Share Posted December 14, 2009 Thanks all for your comments. The engine has been shoved under the bench for the time being as I recently went and bought a new toy (KT 250) which I've been playing with over the last couple of weeks. Anyway, I will drag the engine out again soon as that will be my winter project and I'll have another look at the piston taking on board all your comments. Just one thing, and exuse my ignorance if this is a stupid question, but what exactly is the purpose of the window/s in the rear of the piston and the small holes in the front? Simon Quote Link to comment Share on other sites More sharing options...
b40rt Posted December 14, 2009 Report Share Posted December 14, 2009 forto let gases pass through Quote Link to comment Share on other sites More sharing options...
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